To meet market demands for a great quantity of semiconductor integrated circuits, these circuits are continuously being improved. Take an example of a semiconductor memory. There are various systems of diverse natures, e.g., personal computers, transmitters, TVs, or VTRs., etc., in addition to the main memory units of computers using semiconductor memories.
To meet the requirements of miniaturization, lightness in weight and low power dissipation in these systems, it is required to replace a section where four memories of 64k.times.4 bits were used until now by a single memory of 64k.times.16 bits. For this reason, demand for memories of large capacity and of the multi-bit type is increasing.
In such semiconductor integrated circuits, there are many instances where a current at the time of output increases in proportion to the number of output circuits (output buffers), resulting in a great change (hereinafter referred to as an output noise) in both the power supply potential and the ground potential. Accordingly, in semiconductor integrated circuits where power supply wirings of the output circuit and the internal circuit are commonly used, the internal circuit would be directly affected by the output noise. There is a significant possibility that some erroneous operation in the circuit may take place. As a typical measure to cope with this possibility, there is proposed means to independently provide a power supply wiring for the output circuit, or the like.
FIG. 1 is a block diagram of a semiconductor integrated circuit (semiconductor memory) of the background art wherein respective power supply wirings for the internal circuit and the output circuit are independently provided. This block diagram shows an equivalent circuit of a chip mounted in a package.
In FIG. 1, on the semiconductor chip A, an internal circuit B including an input circuit and an output circuit C are provided. The internal circuit B includes, in addition to the input circuit, other circuits of the semiconductor memory except for the output circuit, e.g., a memory cell array including a plurality of memory cells, a sense amplifier SA, and the like. Storage data in one selected memory cell MC is outputted from the cell through the output circuit C. Power supply pads (power supply terminals) 5 to 8 are provided on the chip. These pads 5 to 8 are connected to the circuits B and C by way of wirings 1 to 4, respectively. The input sides of these pads 5 to 8 are connected to external power supplies V.sub.cc and V.sub.ss through wirings 101 to 104. These wirings 101 to 104 include all the wirings from the external power supplies V.sub.cc and V.sub.ss up to the pads 5 to 8, for example, include inner leads of the package, bonding wires, and the like.
When this device is used, an external pass capacitor C.sub.pass is ordinarily connected between these power supplies V.sub.cc and V.sub.ss. Furthermore, a capacitor C.sub.chip of the chip body is used in the internal circuit B. This capacitor C.sub.chip (through a substrate or the like) is wired between power supplies V.sub.cc and V.sub.ss in the chip. In this example, the elements connected on the output side of the output circuit C are artificially indicated by an output load C.sub.out and resistors R.sub.1 and R.sub.2 connected in series between the power supply V.sub.cc and the ground GND.
The semiconductor integrated circuit of the background art in which the power supply wiring is separated by the internal circuit. The output circuit is constructed as shown in FIG. 1. However, this circuit has the drawbacks described below. Namely, when the output circuit operates, since charges are delivered from the capacitor C.sub.chip via a path including the pad 6, the wiring 2, the wiring 1, and the pad 5, an internal current path is formed within the chip. For this reason, the influence of output noise appears on the power supply wiring for the internal circuit, so it is exerted on the internal circuit B. This phenomenon is accelerated by multi-bit or high speed implementation. For this reason, even if the power supply wiring is simply separated as described above, it is difficult to sufficiently suppress output noise.